Method and installation for packaging a liquid product in a package

ABSTRACT

To package liquids in thin-walled packages while at the same time conferring good mechanical strength upon these packages, an inert gas such as nitrogen and/or carbon dioxide, in the gaseous state is or are introduced into the liquid by means of an injector ( 22 ), the liquid becoming saturated or supersaturated with which gas(es); the product obtained is stored in a reservoir ( 14 ) at a constant level above which an overhead of the said gas is created at a raised pressure which is constant by virtue of regulating means ( 3 ). On demand, this product is transferred, by tapping means ( 4 ), to packages which are partially filled with product the surface of which is surmounted with an overhead of the said gas at a raised pressure after the package has been sealed.  
     Use: packaging of liquids, particularly food liquids.

[0001] The invention relates to the packaging of liquid products inintrinsically deformable packages or containers.

[0002] It consists more particularly in a method and a plant forpackaging liquid products allowing such products, for example liquidfood products, to be packaged in packages or containers with thin walls,without increasing the risk of damage to the package and/or loss ofproduct by comparison with the risks run with packages of greaterthickness.

[0003] What is happening is that with a view to reducing the cost ofpackaging and the weight of such packages, the current trend is forliquids (cordials and other beverages) to be packaged in packages (metaltins known as cans, bottles made of synthetic materials, cartons, etc.)of increasingly thin wall thickness.

[0004] Because of the thinness of the wall, these packages areintrinsically deformable and are tricky to handle and to stack.

[0005] It is known practice for this disadvantage to be overcome byestablishing a raised pressure inside the package while its contents arebeing packaged, this giving it good mechanical strength. This raisedpressure may be obtained by injecting a small amount of inert gas in theliquid state, preferably nitrogen in the liquid state, onto the surfaceof the liquid, for example food liquid, while it is being packaged,between the operation of filling and the operation of sealing thepackage. The disadvantage of this technique is that it is relativelyexpensive.

[0006] It is an object of the invention to overcome this drawback andthe invention therefore relates to a method for packaging liquid productin at least one package, characterized in that an inert gas such asnitrogen and/or carbon dioxide, in the gaseous state, is or are mixedwith a liquid so as to form a product consisting of the liquid saturatedor supersaturated with gas; this product is stored in a buffer reservoirwhich is partially filled with product up to a predetermined level; thislevel is kept approximately constant and, above this level, an overheadof the said gas in the gaseous state, due to the saturation or thesupersaturation, at a predetermined approximately constant raisedpressure; the said product is transferred on demand from the bufferreservoir to the package, open to atmospheric pressure, keeping the saidpredetermined level and the said predetermined raised pressure in thebuffer reservoir so as to partially fill the package with the saidproduct with an overhead of the said gas at a pressure the value ofwhich is approximately equal to that of the overhead in the bufferreservoir, and the package is sealed.

[0007] By virtue of this technique, the cost of raising the pressure ofthe packages is appreciably reduced.

[0008] The method may further have one or more of the followingfeatures:

[0009] when, in the buffer reservoir, the raised pressure of theoverhead of the said gas reaches the predetermined raised pressure, theexcess gas is discharged;

[0010] in order to mix the inert gas and/or the carbon dioxide in thegaseous state into the liquid, this gas is injected into the liquid;

[0011] the raised pressure in the overhead of the buffer reservoir isset to a value lying in the range of 10 mbar to 3 bar;

[0012] the raised pressure is set to a value of about 50 mbar.

[0013] The invention also consists in a plant for packaging liquidproduct in at least one package, characterized in that it comprises afirst circuit in at least part of which a liquid is circulated, a secondcircuit in at least part of which an inert gas such as nitrogen and/orcarbon dioxide, is circulated under pressure in the gaseous state andwhich at outlet comprises an injector opening into an injection zone ofthe first circuit so as to form a product consisting of the liquidsaturated or supersaturated with gas, the first circuit comprising abuffer reservoir into which the said product is introduced, means forkeeping a predetermined level of liquid in this buffer reservoir,control and regulating means for maintaining a predeterminedapproximately constant raised pressure due to the saturation orsupersaturation in the buffer reservoir, and means for tapping from thereservoir in order to transfer the said product from it into the packagewith an overhead at a pressure the value of which is approximately equalto that of the overhead in the buffer reservoir.

[0014] This simple plant combines good reliability with a modest cost.

[0015] The installation may also have one or more of the followingfeatures:

[0016] the first circuit comprises a transfer pump, the inlet of whichis supplied with liquid to be saturated or supersaturated with gas, forcirculating this liquid, and a filling line, the upstream end of whichis connected to the outlet of the pump, an injector belonging to thesecond circuit opening into the line downstream of the pump forinjecting the pressurized gas in the gaseous state thereinto;

[0017] the control and regulating means comprise a regulator, a pressuretransducer measuring the pressure of the gas in the overhead of thereservoir and a level detector detecting the level of the said productin the reservoir, these being connected to the regulator, and aregulator exhaust valve, controlled by the regulator and connected tothe overhead in the reservoir so as to discharge excess gas therefrom onthe command of the regulator;

[0018] the second circuit comprises injection equipment supplying theinjector, and the control and regulating means comprise a regulatorelectrically or pneumatically connected to the injection equipment inorder to transmit to it a signal that regulates the injection; the

[0019] raised pressure kept approximately constant lies within the rangefrom 10 mbar to 3 bar;

[0020] the raised pressure has a value of about 50 mbar;

[0021] the control and regulating means comprise a calibrated safetyvalve connected to the top of the reservoir.

[0022] Other features and advantages of the invention will becomeapparent from the description which will follow of one embodiment of theinvention which is given by way of non-limiting example and illustratedin the appended single FIGURE, which shows a diagram of a plantaccording to the invention.

[0023] The plant depicted in this diagram is a plant for transferringnitrogen or some other inert gas and/or carbon dioxide in the gaseousstate into an aqueous liquid, for example a food liquid intended to forma beverage; in such an application in the food industry, the gas hasbeen filtered and sterilized beforehand, for example using the method inthe French Patent Application published with the number 2 774 006.

[0024] This plant comprises a first circuit 1 comprising, from theupstream end downstream, a transfer pump 11, the inlet of which issupplied with liquid to be laden and here more specifically to besaturated or supersaturated with gas, a filling line 12, the upstreamend of which is connected to the outlet of the pump, a valve 13 insertedin the filling line to allow or prevent flow through this line, and abuffer volume forming a reservoir 14 into which the downstream end ofthe line 12 opens.

[0025] The plant comprises a second circuit 2 supplied with inert gassuch as nitrogen and/or carbon dioxide under pressure in the gaseousstate; this circuit 2 comprises, at outlet, a gas-injecting devicecomprising injection equipment 21 such as that marketed under the name“coffret d'injection Carb'Eco” [Carb'Eco injection kit] by the company“Carboxyque Française” supplying an outlet injector 22 with a nonreturnvalve opening into a zone situated between the transfer pump 11 and thevalve 13 of the filling line 12 pressurized by the pump. The injectionequipment 21 is connected electrically to the pump 11 to receive from ita signal authorizing injection slaving the injection equipment to thepump in such a way in particular that injection of gas is interrupted ifoperation of the pump is stopped.

[0026] The plant also comprises: means 3 for controlling and regulatingthe saturation or supersaturation of the liquid with gas, comprising aregulator 31, such as the one marketed under the name “coffret derégulation Carb'Eco” [Carb'Eco regulating kit] by the company“Carboxyque Française”; a pressure transducer 32 connected by a nozzle321 to the top of the buffer reservoir 14 to measure the gas pressuretherein and which is electrically connected to the regulator 31 totransmit a corresponding measured-pressure signal to it; a leveldetector 33 for detecting the level in the reservoir of the productconsisting of the liquid saturated or supersaturated with gas and whichis also electrically connected to the regulator 31 to transmit acorresponding measured-level signal to it; a regulation exhaust valve 34connected by a pipe 341 to the top of the reservoir to discharge to theoutside any excess gas and which is connected by a conductor 342 ofelectricity to the regulator 31 in order to receive apressure-regulating signal therefrom; and a calibrated safety valve 35connected by a pipe 351 also to the top of the reservoir so as todischarge to the outside any excess gas in the event of a malfunctioningof the regulation.

[0027] The regulator 31 is also electrically or pneumatically connected,on the one hand, to injection equipment 21 to transmit to it a signalthat regulates injection as a function of the measured-pressure signal,and, on the other hand, to the pump 11 to transmit to it alevel-regulating signal designed to modify the output of the pumpaccording to the fluctuations of the level of the saturated orsupersaturated liquid product in the reservoir.

[0028] The plant also comprises tapping means 4 for tapping off liquidproduct from the reservoir on demand so as to transfer this liquidproduct to the packages. These tapping means comprise at least onetapping line 41, in which at least one tapping control valve, notdepicted, is inserted.

[0029] In this plant, the liquid supplied to the pump 11 is circulatedthereby under pressure in the filling line 12, while the gas supplyingthe injection equipment 21 is circulated towards the injector 22 bywhich it is injected in the gaseous state into the injection zone of theline 12 so as to saturate or supersaturate with gas the liquid flowingthrough this line.

[0030] If the valve 13 is open, the product consisting of the liquidsaturated or supersaturated with gas is transmitted to the bufferreservoir 14 where it is kept at a predetermined approximately constantlevel checked constantly by the level detector 33 by an appropriatecommand of the pump 11, so that the reservoir is never completely fulland so that above the free surface of the liquid product there is anoverhead of the gas in the gaseous state initially introduced into theliquid and which has been desorbed during the return to equilibrium ofthe gas which initially saturated or supersaturated the liquid inaccordance with the part pressure of this gas in the buffer volume andits fraction dissolved in the liquid. This overhead consisting of inertgas such as nitrogen and/or of carbon dioxide, in the gaseous state, iskept at a predetermined approximately constant raised pressure checkedconstantly by the pressure transducer 32, by the regulator 31, by meansof the exhaust valve 34 which discharges superfluous gas to outside theplant. If, however, in spite of the regulation, the raised pressureincreases above a certain threshold beyond the raised pressurepredetermined by the control and regulating means, the calibrated valve35 opens and itself discharges the surplus gas to outside the plant.

[0031] Thus, the inert gas and/or the carbon dioxide, in the gaseousstate, is or are mixed with the liquid flowing through the filling line12 and a product consisting of the liquid saturated or supersaturatedwith gas is formed and stored in the buffer reservoir 14. However, thisbuffer reservoir is filled only partially, up to the predetermined levelwhich is kept approximately constant by altering the flow rate throughthe line 12; an overhead consisting of the gas which results from thedesorption of the gas previously injected into the line 12 and mixedwith the liquid is obtained above the free surface of the productconsisting of the liquid saturated or supersaturated with gas; thisgaseous overhead is kept at the predetermined approximately constantraised pressure and liquid product is transferred on demand from thereservoir 14 to one or more packages open to atmospheric pressure,keeping the predetermined level and the predetermined pressure in thereservoir so that the packages are partially filled with product. Afterthis, the packages are sealed and a gaseous overhead at a raisedpressure close to the aforementioned predetermined raised pressure isobtained in these packages.

[0032] The choice of the flow rate of gas injected into the line 12 isdictated by the need to saturate or supersaturate the liquid with thedesired predetermined constant pressure in the overhead of the reservoir14. The relationship, at a given temperature, between the pressure P ofthe gas in the overhead of the reservoir and the concentration x of thegas in the liquid is governed by Henry's law whereby P=H.x where H is acoefficient specific to each gas known as “Henry's coefficient”.

[0033] In the case of the example described and depicted hereinabove,which is that of a food liquid, nitrogen and/or carbon dioxide in thegaseous state is or are injected into the line 12 by means of aninjector 22 so as to obtain, in the overhead of the reservoir 14, aconstant raised pressure at a value preferably lying in the range from10 mbar to 3 bar, for example of more or less 50 mbar, this making itpossible to obtain a raised pressure of a similar value in the packages;thanks to this injection of nitrogen and/or of carbon dioxide, not onlyis the package and its contents stiffened, but the amount of oxygen incontact with the product is also substantially reduced and the risks ofthe product oxidizing are diminished. In addition, the plant accordingto the invention is inexpensive and, in the current state of the art andof costs, the cost of such a plant is about one fifth or one sixth ofthe cost of a conventional plant by means of which liquid nitrogen isintroduced into the packages before they are sealed.

1. Method for packaging liquid product in at least one package,characterized in that an inert gas such as nitrogen and/or carbondioxide, in the gaseous state, is or are mixed with a liquid so as toform a product consisting of the liquid saturated or supersaturated withgas; this product is stored in a buffer reservoir (14) which ispartially filled with product up to a predetermined level; this level iskept approximately constant and, above this level, an overhead of thesaid gas in the gaseous state, due to the saturation or thesupersaturation, at a predetermined approximately constant raisedpressure; the said product is transferred on demand from the bufferreservoir to the package, open to atmospheric pressure, keeping the saidpredetermined level and the said predetermined raised pressure in thebuffer reservoir so as to partially fill the package with the saidproduct with an overhead of the said gas at a pressure the value ofwhich is approximately equal to that of the overhead in the bufferreservoir (14), and the package is sealed.
 2. Method according to claim1, characterized in that when, in the buffer reservoir (14), the raisedpressure of the overhead of the said gas reaches the predeterminedraised pressure, the excess gas is discharged.
 3. Method according toeither one of claims 1 and 2, characterized in that, in order to mix theinert gas and/or the carbon dioxide in the gaseous state into theliquid, this gas is injected into the liquid.
 4. Method according to anyone of claims 1 to 3, characterized in that the raised pressure in theoverhead of the buffer reservoir (14) is set to a value lying in therange of 10 mbar to 3 bar.
 5. Method according to claim 4, characterizedin that the raised pressure is set to a value of about 50 mbar.
 6. Plantfor packaging liquid product in at least one package, characterized inthat it comprises a first circuit (1) in at least part of which a liquidis circulated, a second circuit (2) in at least part of which an inertgas such as nitrogen and/or carbon dioxide, is circulated under pressurein the gaseous state and which at outlet comprises an injector (22)opening into an injection zone of the first circuit so as to form aproduct consisting of the liquid saturated or supersaturated with gas,the first circuit (1) comprising a buffer reservoir into which the saidproduct is introduced, means for keeping a predetermined level of liquidin this buffer reservoir, control and regulating means (3) formaintaining a predetermined approximately constant raised pressure dueto the saturation or supersaturation in the buffer reservoir, and means(4) for tapping from the reservoir in order to transfer the said productfrom it into the package with an overhead at a pressure the value ofwhich is approximately equal to that of the overhead in the bufferreservoir (14).
 7. Plant according to claim 6, characterized in that thefirst circuit (1) comprises a transfer pump (11), the inlet of which issupplied with liquid to be saturated or supersaturated with gas, forcirculating this liquid, and a filling line (12), the upstream end ofwhich is connected to the outlet of the pump, an injector belonging tothe second circuit (2) opening into the line (2) downstream of the pump(11) for injecting the pressurized gas in the gaseous state thereinto.8. Plant according to either one of claims 6 and 7, characterized inthat the control and regulating means (3) comprise a regulator (31), apressure transducer (32) measuring the pressure of the gas in theoverhead of the reservoir (14) and a level detector (33) detecting thelevel of the said product in the reservoir (14), these being connectedto the regulator, and a regulator exhaust valve (34), controlled by theregulator (31) and connected to the overhead in the reservoir (14) so asto discharge excess gas therefrom on the command of the regulator. 9.Plant according to any one of claims 6 to 8, characterized in that thesecond circuit (2) comprises injection equipment (21) supplying theinjector (22), and the control and regulating means (3) comprise aregulator (31) electrically or pneumatically connected to the injectionequipment in order to transmit to it a signal that regulates theinjection.
 10. Plant according to any one of claims 6 to 9,characterized in that the raised pressure kept approximately constantlies within the range from 10 mbar to 3 bar.
 11. Plant according toclaim 10, characterized in that the raised pressure has a value of about50 mbar.
 12. Plant according to any one of claims 6 to 11, characterizedin that the control and regulating means (3) comprise a calibratedsafety valve (35) connected to the top of the reservoir (14).